The invention relates to a relatively quick drying, pliable, and stable modeling dough having a primary binder comprised of an algin, a sugar based polysaccharide, a synthetic resin latex, and filler. Alternatively, a novel surface active drying coating agent may be applied to the subject modeling dough to provide a hardened molded dough resistant to shrinking, flaking, cracking, and crumbling. More specifically, the algin, sugar-based polysaccharide, and synthetic resin latex provide a primary binder for a dough which forms a hard, durable, non-degrading product.
Traditional moldable aqueous compositions and modeling doughs have incorporated starch as a filler material. Such starch based doughs, however, have a tendency to flake, crack, and crumble in both the wet and dry stages. These traditional doughs also typically demonstrate substantial drying shrinkage and discoloration upon drying, as well as leaving a residue on the user""s hands. Put another way, such starch based doughs are characterized by poor plasticity, weak dry strength, and substantial dry shrinkage.
As mentioned above, a central problem with typical water-based doughs is that they experience a loss of volume (shrinkage) upon drying. Because water accounts for a large portion of the volume of the dough in its wet stage, water loss upon drying results in a loss of volume in the resulting molded product. One attempt to overcome the shrinkage problem has been to incorporate large proportions of additional filler such in the dough mixture, but shrinkage still occurs because the volume of the dough decreases as the filler binds together after drying. It has been found that a sculpture made with such a dough can lose about 20% of its total volume upon drying. Moreover, the use of large proportions of filler aggravates the flaking, cracking and crumbling problem discussed above, and also tends to decrease the dry strength of the molded sculpture.
Discoloration upon drying is another problem accompanying typical water-based doughs and is compounded by the dry shrinkage discussed above. As the volume decreases, the relative concentration of pigment increases and the color darkens. In some cases, other components (e.g. a salt) preferentially precipitate and form a crusty, hazy surface on the dried artifact. Still other drawbacks of conventional water-based doughs include the fact that many of them would leave a residue on the user""s hands, and that they can stain or damage textiles, carpets, furniture, etc., with which they come into contact.
Some of the above drawbacks of conventional modeling doughs have been addressed by the development of water-based modeling doughs comprised of a gelled (crosslinked) polymeric resin, water, and a filler material other than starch. More particularly, these later doughs often used poly(vinyl alcohol) (PVA) as the resin, and added a gellant to cause the crosslinking of the poly(vinyl alcohol). The addition of the gellant, and the subsequent crosslinking of the resin, resulted in a cohesive, water-soluble resin system. When the water evaporated, the dried, gelled, polymer resin material system was durable and lightweight. U.S. Patents which relate to gelling the PVA are: U.S. Pat. No. 5,171,766 to Mariano et al., U.S. Pat. No. 5,364,892 to Miller et al., U.S. Pat. No. 5,498,645 to Mariano et al., U.S. Pat. No. 5,506,280 to Miller et al., and U.S. Pat. No. 5,916,949 to Shapero et al., the disclosures of all of which are incorporated herein by reference.
The above four patents all disclose the use of a gelling agent in conjunction with poly(vinyl alcohol) to form a modeling dough. These references teach that the use of a gelling agent, such as a water soluble borate salt, causes the resin to gel (or crosslink). The result, according to these patents, is a modeling dough which demonstrates wet ductility and low stickiness. However, the doughs incorporating poly(vinyl alcohol) often demonstrated poor stability, short use time, and stiffer textures. Also storage stability and usage time become a problem with the use of poly(vinyl alcohol). The storage problem is due in large part to the fact that as time passes the pH of the system decreases. With lowered pH comes a concomitant reduction in crosslink strength which results in a sticky dough, and a sticky dough does not store well.
In sum, poly(vinyl alcohol)/binder based doughs present challenges in the rapid drying of molded products are encountered and suggest the need for a novel modeling composition which exhibits stability and means for preventing dehydration and decomposition. The present invention is directed to a novel modeling dough composition comprised of an algin binder, a polysaccharide binder, and a synthetic latex comprised of emulsions of polyvinyl alcohol, polyvinyl butyral, polyvinyl acetate, and co-polymers thereof. Additionally the invention is directed to a surface active drying coating compositions for moldable doughs and the technique of applying this coating to the instant modeling doughs to form lightweight, hardened, and durable dough models.
It has been found that algin/sugar-based polysaccharide binder based modeling doughs in combination with certain synthetic latex resins will engender stable modeling compositions that have greatly reduced drying times. This enables greater shelf life for these algin/sugar-based polysaccaride binder based modeling doughs as well as increased use time by model makers or children in the case of toy model dough kits. Drying times for these doughs can be further reduced at the point of final use by a coating application to a finished molded article with a novel surface active agent coating composition comprising a molding dough gelling agent and polyvinylpyrrolidone. In this case, the combination of the gelling agent and the polyvinylpyrrolidone at the surface of these modeling dough causes surface linking and interaction of the gellant and polyvinylpyrrolidone with the agglomerate algin/polysaccharide/synthetic resin paricles so as to enhance internal molecular absorbtion of water thereby drying the formed model dough. The blanket coating forms a hard skin on the surface of the dough model resulting in a durable, hard and lightweight model article which prevents any external hydration.
The present invention overcomes the drawbacks inherent in known modeling doughs by a method of making a solid finished model by providing an article of modeling dough comprising a an algin binder, a sugar-based polysaccaride, and synthetic resin latex to form a cohesive resin system. The algin can be any product of marine algae including alginic acid and any salts thereof (e.g. sodium alginate). The algin composition is the water attracting component of the dough and can be alginic acid and any salt or ester thereof. The second major dough component is the larger saccarides known as sugar-based polysaccarides such as polymaltose, polydextrose or corn syrup solids all of which can combine (interlink) with the algin to form aggregate structures. The resin is a synthetic latex solution comprised of emulsions of polyvinyl alcohol, polyvinyl butyral, polyvinyl acetate, and co-polymers thereof. The interaction of the synthetic resin with the algin/sugar-based polysaccharide aggregates forms agglomerates of the three materials which are hydrobinding in nature. The subject matter of the instant invention resides in an improved rapid drying, non-discolorable and non-fading modeling composition for craft articles and toys. An alternative embodiment of the invention is a coating method comprising (i) providing an article of the instant modeling composition and (ii) applying a coating comprised of (a) a gellant for the algin-polysaccharide/binder materials and (b) polyvinylpyrrolidone (xe2x80x9cPVPxe2x80x9d) to the surface of the modeling dough article to form a skin thereon whereby the article is internally dried and rendered hard and durable.
In one preferred form of the instant method, the molding or modeling dough composition so disclosed herein includes from about 0.5% to about 20% total algin, from about 1% to 10% by weight sugar-based polysaccharide resin, from about 5.0 to about 40% water and from about 0.1% to about 3% synthetic latex resin. Optionally, the algin/sugar-based polysaccharide-based composition of the invention may include one or more of a non-algin or non polysaccharide binders such as starch or gums and other additives such as buffering agents, a defoamer, a wetting agent, a humectant, a preservative, a colorant, film formers such as polyvinyl alcohol, and a fragrance. The invention provides a modeling composition which contains readily available components and is non-toxic materials and has sufficient molding properties for modeling craft and toy items. Additionally the instant composition provides a modeling composition which is relatively rapid-drying after modeling so as to generate durable articles. Still further the instant modeling composition is stable after drying and does not exhibit flaking, discoloration, or fadeaway in the modeled article.
The present invention also provides a surface active coating composition for starch-based model articles comprising an aqueous solution of polyvinylpyrrolidone and a generally known gelling or thickening agent for carbohydrate compositions, the most well known being borax salt, such as sodium tetraborate. Preferably the coating composition for the instant algin/polysaccharide based modeling compositons comprises comprising from 1 to 10% sodium tetraborate (Borax), 10 to 30% polyvinylpyrrolidone, 40 to 90% water, and minor amounts of salts, preservatives, and a solvent for the PVP, such as phenoxyethanol,